Azure Front Door To APIM - CORS Error (Cache Not Enabled At Front Door)

Question

Hi,

I have updated few cors origin in APIM policy and while testing getting weird results.

1. When testing from my company network, cors works fine. (internal network flow is App Gateway-->APIM)
2. When testing from internet, cors error is generated that origin is not allowed. (external network flow is Azure Front Door-->App Gateway-->APIM)

First, I suspected that it could be due to caching but I checked, there is no caching enabled at front door, neither at rule engine level nor at routing rule level.
What could be the reason that same client app from same browser invoking same api gets success via app gateway but fails via front door ?

There are no extra header/host settings enabled at front door level.
I am using Front Door Classic

Please guide.